The present invention relates to a thermoelectric module and a thermoelectric device, intended in particular to generate an electric current in a motor vehicle.
In the automotive field thermoelectric devices, also termed thermoelectric generators (TEG), have already been proposed using so-called thermoelectric elements enabling generation of an electric current in the presence of a temperature gradient between two of their opposite faces by the phenomenon known as the Seebeck effect. These devices comprise a stack of first tubes, intended for the circulation of the exhaust gases from an engine, and second tubes, intended for the circulation of a heat transfer fluid from a cooling circuit. The thermoelectric elements are sandwiched between the tubes so as to be subjected to a temperature gradient resulting from the temperature difference between the hot exhaust gases and the cold cooling fluid.
Such devices are of particular interest because they enable production of electricity by conversion of heat coming from the exhaust gases of the engine. They therefore offer the possibility of reducing the fuel consumption of the vehicle through being substituted, at least in part, for the alternator usually provided therein to generate electricity by means of a belt driven by the crankshaft of the engine.
Thermoelectric devices have already been developed including a plurality of thermoelectric modules, each module including thermoelectric elements of annular shape in which the first fluid and the second fluid circulate transversely relative to one another. A thermoelectric module of this kind includes a plurality of thermoelectric elements of annular shape disposed coaxially and longitudinally in line with one another, for example with an alternation of N-type thermoelectric elements and P-type thermoelectric elements. Each thermoelectric element includes fins extending transversely and radially from the exterior periphery. These fins, usually made of aluminum or stainless steel and crimped onto the outside diameter of the rings of the thermoelectric elements, make it possible to promote heat exchanges with the hot exhaust gases that flow across said fins, a cold fluid circulating at the center of the thermoelectric elements, and to extract the maximum heat from the exhaust gases to transfer it to the thermoelectric materials.
Said modules therefore include thermoelectric elements that are assembled in the form of cylindrical pencils and are distributed in a cylindrical enclosure so that the hot exhaust gases circulate freely between the modules while a heat transfer fluid from a cooling circuit circulates at the center of the thermoelectric elements.